This invention pertains to medical prostheses, and in particular, to an artificial heart. In particular, it is conceived to satisfy the current need for creating a new and original design to achieve a Total Artificial Heart in order to replace a native sick heart in its terminal stage or as a bridge to cardiac transplantation or to be used after a heart transplantation failure.
At present, when there is a patient with a serious heart disease, which for different reasons is nonreversible, cardiac transplantation is considered as the solution, provided that the patient gets a donor. However, in the United States, for example, there are about 60,000 patients per year under this situation and only about 6% to 10% get a transplantation due to the current difficulties to find an adequate heart donor.
A Total Artificial Heart (TAH) is recognized as a progress in case of such an extreme situation of a cardiac failure. The present generation of this kind of devices includes the use of different models. In addition, there are partial circulatory assistance devices in use, generally called Left Ventricular Assistance Systems (LVAS).
Under extreme haemodynamic failure circumstances, these devices are used at present as a bridge to transplantation. They permit to keep the patient alive while the patient awaits for the appropriate donor, preventing a serious systemic damage caused by the progressive deterioration of the haemodynamia, which can later compromise the viability of other organs if the patient gets a transplantation.
However, the present Total Artificial Heart generation has had problems. Even though these devices have kept patients alive under extreme circumstances, they have not been able to provide them with an acceptable quality of life.
Most important, due to the disagreement between the sizes of the current generation devices and the space inside the mediastinum available for the current models, i.e. the so called lack of anatomical fit, many of these devices do not place the artificial ventricular and other elements necessary for their operation in an orthotopic position. Several elements are placed outside the body and coupling of parts located both inside and outside of the human body is made through the skin. Several pathological phenomena occur, such as local infections that are later transformed into more serious infections, ascendent infections, skin ulcerations and countless problems for the patient and his/her quality of life. An example of their limitations is the need for the patient to be connected to a pneumatic console. In addition, by placing these parts outside the chest, risks and problems are increased during operation; it also causes surgical complications and problems during the postoperative period such as bleeding, hematomas, infection, and compressions.
Furthermore, due to the reduced space available within the chest, some of the devices of the present generation do not have an adequate size to produce a good final diastolic volume. Hence, often times, in order to obtain an adequate blood flow rate, these devices resort to a significant increase of the heart frequency which causes additional turbulence as a result of and increase in the the blood flow linear velocity. This situation can be the cause of more serious haematological complications, such as haemolysis and bleeding and cause a faster deterioration of the materials that form these devices. On these grounds, a better utilization of the space available inside the mediastinum to achieve a significant increase on the diastolic volume would be highly desirable.
Another type of haematological complications associated with devices of the present generation as thrombosis and embolisms. In some of these devices the internal walls of the cavities through which blood circulates have areas with stasis, corners or boundaries between the different materials of their surfaces and with stitches between them, all of which created a very high embolism risk.
The aforementioned artificial devices present haemostatic complications such as bleeding, occurring because the blood has to go through long circuits of rigid prosthetic tubes with many stitches at each end. These artificial prosthetic tubes do not respond to a need to increase the blood flow rate like native vessels do in reflex mode, i.e. by greatly increasing their diameter. This deficiency causes a larger increase in blood pressure which further stresses the above mentioned stitches and causes the present generation Total Artificial Hearts to operate under more stringent conditions.
Another important problem of these devices is their limitation to compensate the different blood volumes physiologically handled by the pulmonary circuit and the systemic circuit. To alleviate this situation, the surgeon has to create a communication between the two circuits during the implantation surgical procedure, usually making an interauricular communication. However, the size of the surgical opening, in particular and the efficacy of this procedure in general, is often questioned because of frequently occurring systemic or pulmonary hemodynamic congestions.
Accordingly, there remains a need for an artificial heart without the attendant disadvantages of conventionally available artificial hearts.
In general, the present invention comprises an artificial heart that may be implanted in orthotopic position in a circulatory system of a living being, e.g., mammals, that preferrably and anatomically fits within a mediastinum space created by removing at least the two native ventricles, said artificial heart comprising:
one right blood chamber, said right blood chamber having an elongated shape essentially directed up and back, said right blood chamber having one right inlet port for blood to enter, said right inlet port having means for attachment to the right atrium,
one posterior outlet port for blood to exit said right blood chamber, said posterior outlet port being located above and behind the right inlet port, said posterior outlet port having means for attachment to the main pulmonary artery, said posterior outlet port either including or being adjacent to the valve for the main pulmonary artery,
one left blood chamber, said left blood chamber having an elongated shape essentially directed up and to the right, said left blood chamber having one left inlet port for blood to enter, said left inlet port having means for attachment to the left atrium,
one anterior outlet port for blood to exit said left blood chamber, said anterior outlet port being located above and to the right of the left inlet port, approximately at the same height as and in front of said posterior outlet port, said anterior outlet port having means for attachment to the aorta artery, said anterior outlet port either including or being adjacent to the valve for the aorta artery,
the spatial arrangement between said blood chambers being such that, when they are simultaneously fully expanded, a part of the right blood chamber (i.e., which projects onto the anterior thoracic wall and coincides with the projection onto said anterior thoracic wall of a corresponding part of the left blood chamber) is posterior to said corresponding part of the left blood chamber.
In particular, the artificial heart of the instant invention comprises an assembly of two artificial ventricles or blood chambers, each having an inlet and an outlet. The incoming blood from the right auricle enters the right blood chamber through the right inlet port and exits it through the posterior outlet port. The incoming blood from the left auricle enters the left blood chamber through the left inlet port and exits it through the anterior outlet port.
The unique spatial arrangement of both blood chambers, inlet ports and outlet ports give the instant invention a radically better utilization of the space available inside the mediastinum after having surgically removed both native ventricles and having surgically liberated both great vessels, main pulmonary artery and aorta artery. An important advantage of the instant invention consists on the location of the posterior outlet port, which is placed posterior and above to the right inlet port. This specific placement enables the utilization of the space available above both auricles for blood pumping purposes, which otherwise would be unutilized. This arrangement places the posterior outlet port in the space normally occupied by the initial sector of the aorta artery. From that native posterior position, the aorta artery travels upwards and forward to the right to exit the anterior mediastinum. The anterior outlet port is placed approximately at the same height to and in front of the posterior outlet port. Hence, the lower sectors of the aorta artery and main pulmonary artery are surgically liberated and transposed with respect to their antero-posterior position so as to connect them to their corresponding outlet ports. If additional space is desired, the initial sector of both great vessels will be removed and both outlet ports will be placed at a higher position, close to a plane located at the level of the right pulmonary artery and the mid sector of the ascending aorta artery.
Another important advantage of the instant invention consists on the shape and location of both blood chambers which enables a significantly better utilization of the space available in the mediastinum. In their fully expanded position both blood chambers reach the anterior thoracic wall. The right blood chamber has an elongated shape, essentially directed up and back. The left blood chamber has an elongated shape, essentially directed up and to the right. The aorta artery, in its upward path, occupies an anterior position at its crossing of the right pulmonary artery. Therefore, the space available inside the mediastinum is significantly better utilized in the instant invention by keeping the pathway of the blood coming from the right auricle into the main pulmonary artery into an posterior position with respect to the pathway of the blood coming from the left auricle into the aorta artery. Systemic and pulmonary pathways do not comply with this requirement in the native ventricles and the previous art in the field of Total Artificial Hearts has not changed it either. The instant invention changes this native disposition, placing the right blood chamber always behind the left blood chamber, when their projections onto an anterior thoracic wall coincide. In doing so the instant invention is able to utilize the space available for pumping blood and not merely transporting it through artificial tubes to reach its intended destination.
The volume available for pumping in the instant invention is further increased by placing the outlet ports close to the valves leading to the great vessels. Therefore, because of the described arrangement of the different components comprising the instant invention, the pumping volume provided by the blood chambers actually reach higher in the mediastinum than in the previous art.
The better use of the space available in the mediastinum enables the Total Artificial Heart of the instant invention to have a higher final diastolic volume of the blood chambers, obtaining in this way ejected volumes large enough to achieve an acceptable blood flow rate without a significant increase of the heart frequency, and thereby reducing both hemolysis and mechanical wear of movable parts.
Furthermore, in the preferred embodiment of the instant invention and in some variant, this Orthotopic Total Artificial Heart can be completely placed inside the mediastinum, i.e. the blood chambers, the driving mechanism, for example the compressing mechanism, and power source. In this manner, the instant invention can be an integrated, xe2x80x9cone-piecexe2x80x9d system.
The significantly better space utilization of the instant invention is used for at least one of two purposes: a) To place the driving mechanism for the Total Artificial Heart inside the mediastinum; b) To increase the diastolic volume of each blood chamber. This new design realizes a fundamental need expressed by the medical community for the necessary anatomical fit of the Total Artificial Heart with the available and restricted space of the mediastinum.
Due to the different structural layout of the Total Artificial Heart of the instant invention, the following important improvements are made:
1xe2x80x94Keeping the pathway of the blood coming from the right auricle into the main pulmonary artery in a posterior position with respect to the pathway of the blood coming from the left auricle into the aorta artery
2xe2x80x94Outflow tract paths of the artificial ventricles are placed closer to the circulatory system that is going to be irrigated, therefore not needing prosthetic tubes to reach the corresponding arteries.
3xe2x80x94The artificial ventricles are placed in a higher position inside the mediastinum.
4xe2x80x94In the preferred embodiment and other variants of the instant invention, both the outer compressing chamber and the power source are also placed inside the mediastinum.
Furthermore, if necessary, additional space can be conveniently created by resecting the initial sector of the large arterial trunks.
An important hemodynamic and hematological advantage of the instant invention is that, by placing the blood chambers"" outflow near the systemic and pulmonary vascular regions, it no longer requires the use of prosthetic tubes at the outflow of these blood chambers. This characteristic provides the instant invention with the great advantage of being directly connected with the vascular systems through native vessels which respond to increased blood flow with the vasodilatation autonomous reflex response. Hence, no increased pressures are needed to get a higher blood flow, thereby reducing the pressure on the walls of the blood chambers and the turbulence and associated liquid shear stress, all of which greatly reduces the subsequent damage that this causes to blood cells and to the life of the Total Artificial Heart itself.
The artificial ventricles of the instant invention are one-piece blood chambers that have two non-thrombogenetic characteristics, their morphology and their surfaces in contact with the blood. The blood chambers are elongated with an upward shape, having neither stasis areas nor corners or boundaries between dissimilar materials; neither they have stitches among them.
Another advantage of the instant invention is the non-trombogenic walls of the blood chambers. These inner walls are made with biological surfaces, soft and flexible, which protect blood cells and red corpuscles against cellular traumatism, therefore avoiding hemolysis. In addition, the cellular damage is reduced in the instant invention because blood is pumped by the action of forces homogeneously distributed and approximately concentric and also because the blood chambers are elongated and made of a single material without corners, borders or stitches, and without prosthetic materials or tubes of a more or less fixed diameter at the outflow of the blood chambers.
Yet another advantage of the instant invention also provides for the independent variation of the discharging volumes of each blood chamber. Such independent handling of the volumetric flow rates for each blood chamber enables the compensation of the imbalance in the blood flow circulating through the pulmonary circuit and the systemic circuit. Physiological differences and shunts between these circulatory circuits shall be compensated in such a way that there shall be no need for creating surgical shunts.
Additional objects and attendant advantages of the present invention will be set forth, in part, in the description that follows, or may be learned from practicing or using the present invention. The objects and advantages may be realized and attained by means of the instrumentalities, features and/or combinations particularly pointed out in the appended claims. It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not to be viewed as being restrictive of the invention, as claimed.